Re: [PATCH RFC] selinux: provide __le variables explicitly

[Paul Moore]

On Wed, May 8, 2019 at 8:14 PM Nicholas Mc Guire <der.herr@xxxxxxx> wrote:
> On Wed, May 08, 2019 at 05:47:32PM -0400, Paul Moore wrote:
> > On Wed, May 8, 2019 at 2:27 AM Nicholas Mc Guire <hofrat@xxxxxxxxx> wrote:
> > > While the endiannes is being handled properly sparse was unable to verify
> > > this due to type inconsistency. So introduce an additional __le32
> > > respectively _le64 variable to be passed to le32/64_to_cpu() to allow
> > > sparse to verify proper typing. Note that this patch does not change
> > > the generated binary on little-endian systems - on 32bit powerpc it
> > > does change the binary.
> > >
> > > Signed-off-by: Nicholas Mc Guire <hofrat@xxxxxxxxx>
> > > ---
> > >
> > > Problem located by an experimental coccinelle script to locate
> > > patters that make sparse unhappy (false positives):
> > >
> > > sparse complaints on different architectures fixed by this patch are:
> > >
> > > ppc6xx_defconfig
> > >   CHECK   security/selinux/ss/ebitmap.c
> > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > >
> > > Little-endian systems:
> > >
> > > loongson3_defconfig
> > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > >
> > > x86_64_defconfig
> > > security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> > > security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> > >
> > > Patch was compile-tested with: x86_64_defconfig,loongson3_defconfig (both
> > > little-endian) and ppc603_defconfig (big-endian).
> > >
> > > On little-endian systems the patch has no impact on the generated binary
> > > (which is expected) but on the 32bit powerpc it does change the binary
> > > which is not expected but since I'm not able to generate the .lst files
> > > in security/selinux/ss/ due to the lack of a Makefile it is not clear
> > > if this is an unexpected side-effect or due only to the introduction of
> > > the additional variables. From my understanding the patch does not change
> > > the program logic so if the code was correct on big-endian systems before
> > > it should still be correct now.
> >
> > This is a bit worrisome, but I tend to agree that this patch *should*
> > be correct.  I'm thinking you're probably right in that the resulting
> > binary difference could be due to the extra variable.  Have you tried
> > any other big-endian arches?
> >
>
> just tried ppc64_defconfig + AUDIT=y, SECURITY=y, SECURITY_NETWORK=y, SECURITY_SELINUX=y
>
> sparse will complain in the original version about:
>   CHECK   security/selinux/ss/ebitmap.c
> security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> security/selinux/ss/ebitmap.c:389:28: warning: cast to restricted __le32
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
> security/selinux/ss/ebitmap.c:431:23: warning: cast to restricted __le64
>
> which is the same as 32bit ppc - after the patch is applied that is resolved
> and and the generated ebitmap.o files are binary identical.
>
> I just had chosen ppc6xx_defconfig as my big-endian test-target as SELINUX
> was on there by default so I assumed it would be the most reasonable
> compile-test target.

Thanks.

I think this is probably safe to merge once the merge window closes.

-- 
paul moore
www.paul-moore.com